Process for the production of sensitized sheet material

ABSTRACT

A sensitized sheet for a pressure sensitive copy system is obtained by coating the surface of a support with an acceptor composition comprising a particulate mixture comprising an organic acid substance selected from the group consisting of aromatic carboxylic acids and polyvalent metal salts thereof, and an organic high molecular compound. The above coating composition may further contain an inorganic solid particle such as oxides, hydroxides and carbonates of a polyvalent metal, and other mineral pigments. The coating procedure may be carried out with use of coating means mounted on the conventional paper machines.

United States Patent Saito et a1. 1 1 Dec. 2, 1975 15 1 PROCESS FOR THEPRODUCTION OF 3.732.120 5/1973 Brockett ct al 117/362 x SENSITIZED SHEETMATERIAL 3.767.449 10/1973 Hayashi et a1.

3,772,052 11/1973 Kimura et a1. 117/362 [75] Inventors: ToranosukeSaito, Kobe; Jujiro Kohno, Tokatsuki; Daiichiro Tanakaq A1110; ShinlchiOda, Primary Examiner-Thomas J. Herbert, Jr. Amagasaklv of JapanAttorney, Agent, or FirmMcGlew and Tuttle [73] Assignees: Sanko ChemicalCompany Ltd.;

Kanzaki Paper Manufacturing Company Ltd., both of Japan ABSTRACT [22]Filed: Sept. 27, 1973 [21 AppL 401,552 A sensitized sheet for a pressuresensitive copy system is obtained by coating the surface of a supportwith an acceptor composition comprising a particulate mixl30l ForeignApplication Priority Data ture comprising an organic acid substanceselected Sept. 17. 1972 Japan 47-97430 from the group consisting ofaromatic carboxylic acids and polyvalent metal salts thereof, and anorganic high [52] U.S. Cl. 427/147; 427/146; 427/150 molecular compound.The above coating composition [51 Int. Cl. 841M 5/00 may further containan inorganic solid particle such as [58] Field of Search 1 17/368, 36.2.36.7; oxides, hydroxides and carbonates of a polyvalent 427/147, 150,146 metal, and other mineral pigments. The coating procedure may becarried out with use of coating means [56] References Cited mounted onthe conventional paper machines.

UNITED STATES PATENTS 3,689,302 9/1972 Kubo et a1. 117/368 12 Claims, N0Drawings PROCESS FOR THE PRODUCTION OF SENSITIZED SHEET MATERIALBACKGROUND OF THE INVENTION The present invention relates'to asensitized sheet for use in a pressure sensitive copy system andparticularly relates to the sensitized sheet having a coating comprisingan acceptor which is capable of color forming when coming into contactwith a colorless chromogenic compound.

Generally, the pressure sensitive copy system of the invention utilizesa color forming reaction between an electron donating colorless compoundand an electron accepting solid acid.

Various types of pressure sensitive recording sheets are hitherto knownin the prior art. For example, US. Pat. No. 2,730,456 discloses atransfer type of the pressure sensitive recording sheets wherein anupper sheet or overlying sheet is coated with a layer containingmicro-capsules in which an electron donating colorless compound(hereinafter referred to as color former) dissolved in an oily solventis enveloped, and an underlying sheet is sensitized with a coating layercontaining an electron accepting solid acid (hereinafter referred to asacceptor). The color former transfers into the underlying sheet uponrupture of the micro-capsules and forms a visible colored image on theunderlying sheet. If multiple copies are desired, an intermediate sheetcarrying the micro-capsules on one side and the acceptor on the otherside is inserted between the upper sheet and the underlying sheet.

Also, U.S. Pat. No. 2,730,457 discloses a recording sheet wherein bothof the fine capsules and acceptor are coated on the same side, so calledself contained copying sheet".

Furthermore, German Pat. No. 1,275,550 discloses a pressure sensitiverecording sheet wherein a record forming components soluble in a liquidsolvent is carried on the surface and/or inside of a support and saidsolvent is present isolated from at least one of said record formingcomponents by pressure-rupturable capsules.

Examples of the color former include Leuco type of chromogenic compoundssuch as Crystal Violet Lactone, Benzoyl Leucomethylene Blue, MalachiteGreen Lactone, Rhodamine B Lactone, fluoran derivatives andspiropyranes.

Known acceptors include acid clay, activated clay, attapulgite, kaolinand other inorganic solid acids, but there are disadvantages that adeveloped color image is faded by the action of moisture and sunlight. Asensitive sheet coated with organic solid acid such as phenolic resinsis also used. However, such a sheet is apt to yellow by the sunlight andthe developed color image is decreased in density or allowed todisappear for a little while by heat or moisture.

As another example of the organic solid acid, aromatic carboxylic acids(U.S. Pat. Nos. 3,322,557 and 3,488,207) and polyvalent metal salts ofaromatic carboxylic acid (DT-OS 2,152,765) are proposed. There are, forexample, described benzoic acid, omitrobenzoic acid, o-chlorobenzoicacid, 4-methyl-3-nitroben-.

zoic acid, p-isopropylbenzoic acid, p-terL-butylbenzoic acid,salicylicacid, 5-tert.-butylsalicylic acid, 3- cyclohexylsalicylic acid,3-methyl-5-isoamylsalicylic acid, 3,5-dinitrosalicylic acid, l-naphthoicacid, 1- hydroxy-Z-naphthoic acid, 5,5-methylen-disalicylic acid and theother similar aromatic carboxylic acids, and salts of metals such asmagnesium, calcium, zinc, cadmium, aluminum, gallium, tin, lead,chromium, molybdenum, manganese, cobalt and nickel with the abovecarboxylic acids. Such aromatic carboxylic acids and polyvalent metalsalts thereof are superior in stability toward the sunlight to thephenolic resins. Some of the aromatic carboxylic acids and polyvalentmetal salts thereof have a sublimating property, and therefore a sheetsensitized by a coating containing such acceptors loses a color-formin gability with the lapse of time. Since the said acceptors are relativelysoluble in water and thus diffuse within the sheet by the action of highmoisture or water, the color-forming ability is lost on the surface ofthe sheet. Such disadvantages show an increasing tendency as themolecular weight of aromatic carboxylic acid is lowered. The reason whysaliv thereof show improved resistance toward heat and moisture as themolecular weight increases and can maintain relatively stablecolor-forming properties at normal temperature and humidity. Thepressure sensitive recording papers, however, leave room for furtherimprovements of the properties to be required in practice. It isunavoidable that the recording papers are stored and handled under thecondition of high humidity or water attaches directly to the sheet. Forexample, it often occurs that rainwater or water spilt from a glassattaches to the sheet. In some cases, when a letter or figure is printedby offset printing on the upper or underlying sheet of pressuresensitive recording papers, fountain solution on the blanket transfersonto an acceptor coated surface of the sheet. Under such circumstance,if an organic acid substance has insufficient resistance toward highmoisture or water, a sensitized sheet is markedly reduced in thecolor-forming ability or in case the sensitized sheet is in touch with asheet carrying the encapsulated color former the organic acid substancecomes into contact with the color former by means of the moisture orwater as a carrier and thus there arises undesirable color which is socalled smudge.

Accordingly, a coating layer containing the acceptor must have a highhumidity or water resistance sufficient to maintain stabilities of thecolor-forming ability and developed color image and to inhibit thesmudge.

On the other hand, a coating composition containing aromatic carboxylicacids and polyvalent metal salts thereof, because of being unstabletoward heat in general, needs a careful watch and handling duringstorage or coating procedure. Particularly, in the coating procedure thecoating composition is subject to mechanical shear and accompanied by arising temperature. Therefore, when a mechanical and thermal stabilityis insufficient, the coating composition cannot form a uniform layer onthe surface of a base sheet and in the worst case it is unavoidable todiscontinue the coating procedure. If the coating procedure is efi'ectedby a coating apparatus mounted on a paper machine, it is the mostsimplified process and therefore advantageous economically. ln this casesince the coating composition is coated on the base sheet preheated by adryer, the mechanical and thermal stability requirements become moresevere.

SUMMARY OF THE INVENTION It is, therefore, an object of this inventionto provide a sensitized sheet for a pressure sensitive copy systemhaving excellent resistance toward heat, light and particularly a highhumidity or water and capable of maintaining a stable color-formingability.

It is another object of this invention to provide acceptor coatingcomposition having an excellent mechanical and thermal stability.

It is still another object of this invention to provide a process forthe preparation of a sensitized sheet in the most effective way.

Other objects and advantages of this application will appear from thedetailed description to follow.

The foregoing and other objects of this invention are attained in asensitized sheet, for use in a pressure sensitive copy system, having acoating comprising an acceptor, the acceptor being a particulate mixtureof (a) an organic acid substance selected from the group consisting ofaromatic carboxylic acids and polyvalent metal salts thereof, and (b) anorganic high molecular compound.

The mixture of the organic acid substance and organic high molecularcompound can be pulverized to uniform fine powders of several microns inparticle size by mechanical means, for example ball-milling. A coatinglayer having the fine powders homogeneously dispersed therein isobtained and therefore the distinct images are obtained.

DETAILED DESCRIPTION OF THE INVENTION The organic acid substance to beused in the invention is selected from the group consisting of aromaticcarboxylic acids and polyvalent metal salts thereof. The aromaticcarboxylic acids and polyvalent metal salts thereof useful for theacceptor are in detail explained in US. Pat. application Ser. No.265,484, filed June 23, 1972, now abandoned, which discloses thepressure sensitive record system. These compounds are illustrated bynon-limitative examples as given hereunder, but it should of course beunderstood that other aromatic carboxylic acids and polyvalent metalsalts thereof, capable of color forming when brought into contact with acolor former may be also used.

An aromatic carboxylic acid to be used is represented by the formula 1,

COOH

wherein R,, R R R and R each represents hydrogen, halogen or a hydroxyl,amino, carboxyl, carbamoyl, N-substituted carbamoyl, alkyl, cycloalkyl,alkoxyl, aryloxy, aralkyl or alkylaryl group, and any adjacent pair ofR, to R, can, together with the carbon atoms to which they are attached,complete a ring. Compounds of formula I wherein R, or R is a hydroxylgroup are especially important in embodiments of the invention asmentioned in detail hereinafter.

Examples of aromatic carboxylic acids of formula I wherein R, and R arenot a hydroxyl group include benzoic acid, o-toluic acid, m-toluic acid,p-toluic acid, p-tert.-butylbenzoic acid, o-chlorobenzoic acid,mchlorobenzoic acid, p-chlorobenzoic acid, dichlorobenzoic acid,trichlorobenzoic acid, tetrachlorobenzoic acid, phthalic acid,isophthalic acid, terephthalic acid, Z-carboxybiphenol, p-oxybenzoicacid, paramethoxybenzoic acid, p-butoxybenzoic acid, p-octoxybenzoicacid, gallic acid, anthranilic acid, phthalic acid monoamide, phthalicacid monoanilide, 3-tert.-butyl-4- hydroxybenzoic acid,3-cyclohexyl-4-hydroxybenzoic acid, 3-phenyl-4-hydroxybenzoic acid,3-(0z-methylbenzyl)-4-hydroxybenzoic acid, 3,5-dimethyl-4-hydroxybenzoic acid, trimellitic acid, pyromellitic acid, a-naphthoicacid, ,B-naphthoic acid, tetrachlorophthalic acid and2,2-dicarboxydiphenyl.

Aromatic carboxylic acids of formula I wherein R, or R is a hydroxylgroup are defined by formula II,

COOH R OH wherein R to R are as defined in R, to R of formula I.

Examples of such carboxylic acids include salicylic acid, o-cresotinicacid, p-cresotinic acid, 3-ethylsalicylic acid, 4-ethylsalicylic acid,3-isopropylsalicylic acid, 4-isopropylsalicylic acid,5-isopropylsalicylic acid, 3- tert.-butylsalicylic acid,5-tert.-butylsalicylic acid, 3- cyclohexylsalicylic acid,5-cyclohexylsalicylic acid, 3- phenylsalicylic acid, S-phenylsalicylicacid, 3-benzylsalicylic acid, 5-tert.-octylsalicylic acid,3-(a-methylbenzyl) salicylic acid, S-(a-methylbenzyl) salicylic acid,5-nonyl salicylic acid, 5-(oz,a-dimethylbenzyl) salicylic acid,5-chlorosalicylic acid, S-butoxysalicylic acid and 5-octoxysalicylicacid.

Compounds of formula II wherein R and R are halogen, alkyl, cycloalkyl,aryl, aralkyl or alkylaryl can be easily derived in commercial scalesfrom phenols, alkylphenols, arylphenols or halogenated phenols. Examplesof such aromatic carboxylic acids include 3,5- dichlorosalicylic acid,3-chloro-5-tert.-butylsalicylic acid, 3-chloro-5-tert.-amylsalicylicacid, 3-chloro-5- tert.-octylsalicyclic acid, 3-chloro-5-(a,a-dimethylbenzyl) salicylic acid, 3,5-dimethylsalicylic acid,3-methyl- 5-tert.-butylsalicylic acid, 3-methyl-5-cyclohexylsalicylicacid, 3-methyl-5-tert.-octylsalicylic acid, 3-methyl- S-(a-methylbenzyl)salicylic acid, 3-methyl-5-nonylsalicylic acid,3-methyl-5-(a,a-dimethylbenzyl salicylic acid, 3,5-diisopropylsalicylicacid, 3,5-di-sec.-butylsalicylic acid, 3-tert.-butyl-5-chlorosalicylicacid, 3-tert.- butyl-S-methylsalicylic acid,3-tert.-butyl-5-ethylsalicylic acid, 3,5-di-tert.-butylsalicylic acid,3-tert.-butyl-5- cyclohexylsalicylic acid,3-tert.-butyl-5-phenylsalicylic acid,3-tert.-butyl-5-(4'-tert.-butylphenyl)salicylic acid,3-tert.-amyl-5-chlorosalicylic acid, 3-tert.-amyl-5- methylsalicylicacid, 3-tert.-amyl-5-ethylsalicylic acid, 3,5-di-tert.-amylsalicylicacid, 3-tert.-amyl-5-cyclohexylsalicylic acid,3-tert.-amyl-5-phenylsalicylic acid, 3-tert.-amyl-5-(4'-tert.-amylphenyl) salicylic acid, 3-cuclohexyl-S-chlorsalicylic acid, 3-cyclohexyl-5- methylsalicylic acid,3-cyclohexyl-S-ethylsalicylic acid, 3,5dicyclohexylsalicylic acid,3-cyclohexyl-5-phenylsalicylic acid, 3-cyclohexyl-5-(4-cyclohexylphenyl)salicylic acid, 3-phenyl-5-chlorosalicylic acid,3-phenyl-S-isopropylsalicylic acid, 3-phenyl-5-tert.-butylsalicylicacid, 3-phenyl-5-tert.-amylsalicylic acid, 3-phenyl--cyclohexylsalicylicacid, 3-phenyl-5-benzylsalicylic acid, 3-phenyl-5-tert.-octylsalicylicacid, 3-phenyl- S-(a-methylbenzyl) salicylic acid,3-phenyl-5-nonylsalicylic acid, 3-phenyl-5-( apt-dimethylbenzyl) salicylic acid, 3-benzyl-5'chlorosalicylic acid, 3-benzyl-5- methylsalicylicacid, 3-benzyl-S-ethylsalicylic acid, 3- benzyl-5-cyclohexylsalicylicacid, 3'benzyl5-phenylsalicylic acid, 3,5-dibenzylsalicylic acid,3-benzyl-5- tert.-octylsalicylic acid, 3-benzyl-5-nonylsalicylic acid,3-benzyl'5-(mar-dimethylbenzyl) salicylic acid, 3-tert.-octyl-S-chlorosalicylic acid, 3-tert.-octyl-5 methylsalicylic acid,3-tert.-octyl-5-ethylsalicylic acid, 3-tert.-octyl-S-cyclohexylsalicylic acid, 3-tert.-0ctyl-5-phenylsalicylic acid,3,5-di-tert.-octylsalicylic acid, 3-(amethylbenzyl)-5-chlorosalicylicacid, 3-(a-methylbenzyl)-5-methylsalicylic acid, 3-(a-methylbenzyl)-5-ethylsalicylic acid, I 3-(a-methylbenzyl)-5-cyclohexylsalicylic acid,3-(a-methylbenzyl)- S-phenylsalicylic acid, 3,5-di(a-methylbenzyl)salicylic acid, 3-( a-m'cthylbenzyl)-5-( a,a-dimethylbenzyl) salicylicacid, 3-(a-methylbenzyl)-5-{4-(oz-methylbenzyl) phenyl} salicylic acid,3-nonyl-5-chlorosalicylic acid, 3-nonyl-5-methylsalicylic acid,3-nonyl-5-ethylsalicylic acid, 3-nonyl-5-phenylsalicylic acid,3,5-dinonylsalicylic acid, 3-(a,a-dimethylbenzyl)-5-chlor0salicylicacid, 3-(a,a-dimethylbenzyl)-5-methylsalicylic acid,3-(a,adimethylbenzyl)-5-ethylsalicylic acid, 3-( a,a-dimethylbenzyl)-5-t-amylsalicylic acid, 3-(a,a-dimethylbenzyl 5-cyclohexylsalicylicacid, 3-(a,a-dimethylbenzyl)-5- phenylsalicylic acid, 3-(a,adimethylbenzyl)-5-( a-methylbenzyl) salicylic acid, 3,5-di(a,adimethylbenzyl)salicylic acid, 3-(4'-tert.-butylphenyl )-5-tert.-butylsalicylic acid,3-( 4 '-cyclohexylphenyl)-5-cyclohexylsalicylic acid and3-{4'-(a,adimethylbenzyl) phenyl}-5-(a,a-dimethylbenzyl) salicylic acid.

Aromatic carboxylic acids of formula ll in which R or R is alkyl,cycloalkyl or phenyl can be derived from, for example, metracresol,metapropylphenol, metaphenylphenol, 2,3-xylenol, 2,5-xylen0l,3,4-xylenol and 3,5-xylen0l. Examples of such carboxylic acids include3,4-dimethylsalicylic acid, 4,5-dimethylsalicylic acid,4,6-dimethylsalicylic acid, 4-methyl-5-isopropylsalicylic acid,4-methyl-5-sec.-butylsalicylic acid, 4-methyl- 5-tert.-butylsalicylicacid, 4-methyl-S-terL-amylsalicylic acid, 4-methyl-5-cycl0hexylsalicylicacid, 4-methyl- S-benzylsalicylic acid, 4-methyl-5-tert.-octylsalicylicacid, 4-methyl-5-(a-methylbenzyl) salicylic acid, 4- methyl-S-nonylsalicylic acid, 4-methyl-5-(a,a-dimethylbenzyl) salicylic acid,3,6-dimethylsalicylic acid, 3- tert.-butyl-6-methylsalicylic acid,3-tert.-amyl-6- methylsalicylic acid, 3-cyclohexyl-6-methylsalicylicacid, 3-tert.-octyl-6-methylsalicylic acid,3-(a-methylbenzyi)6-methylsalicylic acid, 3,6-diisopropylsalicylic acid,3-tert.-butyl-6-isopropylsalicylic acid, 3-tert.-octyl--isopropylsalicylic acid,3-(a,oz-dimethylbenzyl)-6-isopropylsalicylic acid,3-tert.-butyl-6-phenylsalicylic acid, 3-tert.-amyl-6-phenylsalicylicacid, 3- cyclohexyl-6-phenylsalicylic acid, 3-tert.-octyl-6-phenylsalicylic acid, 3-(a-methylbenzyl)-6-phenylsalicylic acid or3-(a,a-dimethylbenzyl)-6-phenylsalicylic acid.

Aromatic carboxylic acids of formula II in which at least one of R to Ris a hydroxyl group are presented by formula III,

COOH

OH I (III) 3 ,S-di-cyclohexyl-6-hydroxysalicylic acid, 3 ,5- di(a-methylbenzyl )-6-hydroxysalicylic acid, 3 ,5-di(a,a-dimethylbenzyl)-6-hydroxysalicylic acid, 5-

hydroxysalicylic acid, 4-tert.-butyl-5-hydroxysalicylic acid,4-tert.-amyl-5-hydroxysalicylic acid, 4-cyclohexyl-S-hydroxysalicylicacid, 4-(a-methylbenzyl)-5- hydroxysalicylic acid,3,6-diisopropyl-S-hydroxysalicylic acid,3,6-dicyclohexyl-S-hydroxysalicylic acid or 3,6-di(a-methylbenzyl)-5-hydroxy-salicylic acid.

As the case that any adjacent pair of R to R form a ring together withthe carbon atoms to which they are attached, there are naphthalenederivatives. They are represented by formulae IV, V and Vi,

COOH

7 3'8 t R'7 coon R'6 I on R's R'3 R'6 coon I R 5 on wherein R,, R' R;,,R',,, R' R' R and R each is hydrogen, halogen or a hydroxyl, alkylcycloalkyl or aralkyl group. As examples of such naphthalenederivatives, there are indicated l-hydroxy-2-carboxynaphthalene,l-hydroxy-2-carboxy-4-isopropylnaphthalene,lhydroxy-Z-carboxy-4-cyclohexylnaphthalene,l-hydrogen-Z-carboxy-4-benzylnaphthalene,l-hydroxy-Z-carboxy-4-(a-methylbenzyl) naphthalene, l-hydroxy-2-carboxy-7-isopropylnaphthalene,l-hydroxy-Z-carboxy-7-tert.-butylnaphthalene, l-hydroxy-2-carboxy-7-tert.-amylnaphthalene, 1-hydroxy-2-carboxy-7- cyclohexylnaphthalene,1-hydroxy-2-carboxy-7-tert.- octylnaphthalene, l-hydroxy-2-carboxy-7-(a-methylbenzyl) naphthalene, l-hydroxy-2-carboxy'7-(a,adimethylbenzyl) naphthalene,lhydroxy-Z-carboxy-4,7-diisopropylnaphthalene, 1-hydroxy-Z-carboxy-4.7-di-tert.-butylnaphthalene.lhydroxy-Z-carboxy-4,7-di-tert.-amylnaphthalene,lhydroxy-2carboxy-4,7-dicyclohexylnaphthalene, lhydroxy-Z-carboxy-4,7-dibenzylnaphthalene,lhydroxy-Z-carboxy-4,7-di-tert.-octylnaphthalene,lhydroxy-2-carboxy-4.7-di(a-methylbenzyl) naphthalene, l-hydroxy-Z-carboxy-4,7-di(a,a-dimethylbenzyl) naphthalene, l-carboxy-2hydroxynaphthalene. l-carboxy-2-hydroxy-3,6,8-tri-tert.-butylnaphthalene, 2-hydroxy-3-carboxynaphthalene, 2-hydroxy-3carboxy-6,8-di-tert.-butylnaphthalene, 2-hydroxy-3-carboxy6.8-di-tert.-amylnaphthalene, 2-hydroxy-3-carboxy-6,8-dicyclohexylnaphthalene, 2-hydroxy-3-carboxy-6,8-di-tert.-octylnaphthalene, 2-hydroxy-3-carboxy- 86,8-di(a-methylbenzyl) naphthalene or 2-hydroxy-3-carboXy-6,8-di(a,a-dimethylbenzyl) naphthalene.

Aromatic carboxylic acids derived from, for example, bisphenol A,4,4-dihydroxycyclohexylidenebiphenyl, 4,4'dihydroxymethylenebiphenyl and2,2dihydroxydiphenyloxide are regarded as condensates of salicylic acid.Examples of these carboxylic acids include 5-(4'-hydroxybenzyl)salicylic acid, 5-(3'-carboxy-4- hydroxybenzyl) salicylic acid(methylene-bis-salicylic acid),3-tert.-butyl-5-(3,5-di-tert.-butyl-4-hydroxybenzyl) salicylic acid,3-(a,a-dimethylbenzyl)-5- {3,5'- di( 0:,oz-dimethylbenzyl -4 -hydroxybenzyl} salicylic acid, 3-tert.- butyl-5-( a,a-dimethyl-3 ,5'-di-tert.-butyl-4 -hydroxybenzyl) salicylic acid,5-(a,a-dimethyl-3-carboxy-4'- hydroxybenzyl) salicylic acid,5-(a,a-dimethyl-4- hydroxybenzyl) salicylic acid, 3-(2-hydroxyphenoxy)salicylic acid, 3-(2-hydroxy-3-carboxyphenoxy) salicylic acid, 3-( 2-hydroxy-3 -carbo xy-S -tert.-butylphenoxy)-5-tert.-butylsalicylic acid,3-(2-hydroxy-3,- 5'-di-tert.-butylphenoxy)-5-tert.-butylsalicylic acid,3- {2 '-hydroxy-3 '-carb0xy-5 a,a-dimethylbenzyl) phenoxy}-5-(a,a-dimethylbenzyl) salicylic acid, 3-{ 2-hydroxy-3 ,5 -di(a,o-dimethylbenzyl) phenoxy} (a,a-dimethylbenzyl) salicylic acid or3-(2-hydroxy- 3,5'-dicyclohexylphenoxy)-5-cyclohexylsalicylic acid.

Furthermore, a large number of aromatic carboxylic acids of formula IIwhich are difficult to be expressed in the chemical nomenclature arelisted. For instance, there are indicated condensation products offormaldehyde with salicylic acid or nucleus-substituted salicylic acidsand phenols, salicylic acid or nucleus-substituted salicylic acidadducts of propylene polymer or isobutylene polymer, salicylic acid ornucleus-substituted salicylic acid adducts of benzylchloridepolycondensation products, salicylic acid or nucleus-substitutedsalicylic acid adducts of styrene polymers, salicylic acid ornucleus-substituted salicylic acid adducts of a-methylstyrene polymers,salicylic acid or nucleus-substituted salicylic acid condensates ofaldehydes or acetylene, salicylic acid or nucleus-salicylic acidcondensate of ketones, and salicylic acid or nucleus-substitutedsalicylic acid adducts of compounds having an unsaturated bond.

The terms of aromatic carboxylic acids" and polyvalent metal saltsthereof" used herein and in the claims include also the condensates andpolymerizates as mentioned above and polyvalent metal salts thereof.

All of the above aromatic carboxylic acids can form salts withpolyvalent metals.

Polyvalent metals which are concerned with the acceptors of the presentinvention represent all the saltforming metals other than lithium,sodium, potassium, rubidium, cesium and francium. The useful polyvalentmetals include magnesium, aluminum, calcium, scandium, titanium,vanadium. chromium, manganese, iron, cobalt, nickel, copper, zinc,gallium, germanium, strontium, yttrium, zirconium, niobium, molybdenum,silver, cadmium, indium, tin, antimony, barium, tungsten, mercury, leadand bismuth. Further, most suitable metals for the practical use of themare magnesium, aluminum, calcium, titanium, manganese, zinc and tin.

Among the above-mentioned aromatic carboxylic acids and polyvalent metalsalts thereof, compounds having at least one hydroxyl group on thebenzene ring. particularly a hydroxyl group at the ortho-position to thecarboxyl group are preferred from the point of view of color-formingability. From aspects of the heat and moisture resistances and thecompatibility with an organic high molecular compound, an aromaticcarboxylic acid and polyvalent metal salt thereof, having highermolecular weight are preferred, that is, ones having 10 or more,preferably 17 or more carbon atoms in total are recommended.Particularly, compounds of formulae II, III, IV, V and VI in which 3position to the carboxyl group is substituted with isopropyl, secondarybutyl, tert.butyl, tert.-amyl, cyclohexyl, phenyl, substituted phenyl,benzyl, a-methylbenzyl, a,a-dimethyl benzyl, tert.-octyl, nonyl and theother group having 3 or more carbon atoms show excellent color-formingproperties, stability toward water and compatibility with an organichigh molecular compound. Compounds of formulae II, III, IV, V and VIbearing at least one of S-membered and 6-membered carbon-rings assubstituents and having 17 or more carbon atoms in total are mostpreferred.

The polyvalent metal salts of aromatic carboxylic acid are obtained byreaction of aromatic carboxylic acids with oxides, hydroxides,carbonates and silicates of polyvalent metals, though they areconveniently obtained by a double decomposition of an alkali metal saltof aromatic carboxylic acid and a water soluble polyvalent metal salt.In this case the aromatic carboxylic acid and water soluble polyvalentmetal salt each may be used alone or in mixture of two or more. Thepolyva lent metal salts of aromatic carboxylic acid are usually obtainedin form of crystalline powders, amorphous fine powders or viscousliquids.

An organic high molecular compound used in the invention should show aneasily non-fluidifying property at normal temperature and preferably isselected from ones having a molecular weight of about 400 or more. Thefollowing are examples of useful organic high molecular compounds:Polybutadiene, butadiene copolymers such as butadiene-isoprene copolymerand butadiene-styrene copolymer, cyclopentadiene polymers,cyclopentadiene copolymers, polystyrenes, styrene copolymers,a-methylstyrene polymers, a-methylstyrene copolymers, polyvinylchloride, vinylchloride copolymers, vinylidenechloride copolymers,polychloroprene (Neoprene), acrylic ester polymers, acrylic estercopolymers, acrylic acid copolymers, methacrylic ester polymers,methacrylic ester copolymers, methacrylic acid copolymers, vinylacetatepolymers, vinylacetate copolymers such as ethylene-vinylacetatecopolymer, acrylonitrile copolymers, acrylamide copolymers, allylalcoholcopolymers, benzylchloride polycondensation products, benzylchloridecopolycondensation products, meta-xylene-formaldehyde condensates,diphenyl-formaldehyde condensates, diphenyl-metaxylene-formaldehydecopolycondensation products, phenol-formaldehyde condensates,substituted phenolformaldehyde condensates,phenol-meta-xylene-formaldehyde condensates, the other phenolcopolycondensation products, the other substituted-phenol copolymers,polyester resins, melamine resins, polycarbonate resins, butyral resins,nitrocellulose, ethylcellulose, shellac, gilsonite, dammar. Styrenepolymers, styrene copolymers, a-methylstyrene polymers, a-methylstyrenecopolymers and substituted phenolformaldehyde polymerizationcondensation products are preferred. These high molecular compounds havegood compatibility with various types of the organic acid substance andtherefore are easily pulverized to fine powders, and maintain a goodcolor'forming property.

It is desirable for the above mentioned organic high molecular compoundto be selected from compounds having compatibility with the organic acidsubstance to be incorporated therein. The term of compatibility usedherein means such property that two or more chemical substances dissolvewith one another and also such property that the dissolution occurs onlyin the one because of the other being crystalline.

In many cases, the compatibility of a chemical substance may beexplained in relation with polarity of the substance. A suitablecombination of the organic acid substance and high molecular compound inthe present invention will be determined taking this point of view intoconsideration. Generally speaking, the polarity of chemical substance isqualitatively understood in the light of the balance between aninorganophile and an organophile. An aromatic carboxylic acid is usuallyincreased in the organophile and lowered in the polarity as the numberof carbon atoms becomes large. In the case of aromatic carboxylic acidshaving the same number of carbon atoms, as polar radicals such ashydroxyl, carboxyl, nitro, cyano, and halogen are introduced into themolecule, the polarity becomes higher. The polarity may also varydepending upon the type of radicals and the position of radicals in themolecular. Types of polyvalent metals have influence on thecompatibility which may be explained in relation with the polarity. Forexample, many of polyvalent metals which tend to form polyvalent metalsalts having a high inorganophile or high polarity are metals with arelatively small atomic weight such as magnesium, aluminum, calcium andtitanium. To the contrary, zinc and tin tend to form polyvalent metalsalts with low inorganophile or low polarity. On the other hand, in caseof organic high molecular compounds, when, for example, polyethylene andpolypropylene which are regarded as being of the lowest polarity areintroduced with double bond or substituted with halogen, benzene ring orhydroxyl, carboxyl, ether, ester, ketone, nitro, cyano and amideradicals, the polarity increases depending upon the type and number ofthe substituents.

As substances having similar polarity are compatible or miscible witheach other, a pulverized homogeneous mixture comprising an organic acidsubstance and organic high molecular compound is obtained by selectingthe organic high molecular compound having the similar polarity to thatof an aromatic carboxylic acid and polyvalent metal salt.

An organic high molecular compound compatible with an organic acidsubstance of a relatively high polarity is selected from one with a highpolarity which bears polar radicals in the molecule. However, if suchradicals as --C E N, -C0, -N=, --SO SO--, S-, PO=, P=, CS- and O arepresent in large numbers in the molecule, they obstruct the colorforming reaction with a color former and therefore, it is desirable toconfine the introduction of such radicals to the irreducible minimum ofa demand. Halogen and a phenyl radical show no obstacle to the colorreaction. Particularly, hydroxyl and carboxyl radicals have no obstacleto the color reaction and raise the polarity in the presence of a smallnumber of radicals.

Though an incorporation ratio of the organic high molecular compound tothe organic acid substance is not particularly limited, when the amountof the former is too little. the desired resistance toward heat, lightand particularly a high moisture or water cannot be attained. It isdesirable to incorporate the organic high 1 1 molecular compound in theamount of 5 parts by dry weight or more, preferably from to 300 parts byweight based upon 100 parts by dry weight of the organic acid substance.

There are many methods for obtaining a pulverized mixture comprising theorganic acid substance and organic high molecular compound. For example,the most simple and preferable method includes the steps of mixing andmelting the organic high molecular compound and organic acid substancewhile heating, solidifying the resultant by cooling and then pulverizingit. Another method includes the steps of dissolving the organic acidsubstance and high molecular compound in an organic solvent therefor andmixing same, evaporating the resultant to dryness and then pulverizingit. The pulverizing may be effected in a dry system or in a wet systemwith a medium such as water. In this case surface active agents and finepowders with high hardness such as silicic anhydride and kaolin may beallowed to co-exist in order to raise pulverization efficiency.

As the organic high molecular compound used in the above describedmethods, one having a relatively high glass transition point (secondorder transition point) and a relatively low molecular weight, ispreferred. It is, in general said that an organic high molecularcompound having a large number of ring-structures in the molecule showsa high second order transition point. There are, for example, indicatedpolystyrene, styrenea-methylstyrene copolymers, a-methylstyrenepolymers, cyclopentadiene copolymers, aliphatic unsaturated cyclichydrocarbon polymers, benzylchloridediphenyl poly-condensation products,meta-xylene-formaldehyde poly-condensation product,meta-xylenediphenyl-formaldehyde copolycondensation products,meta-xylene-alkylphenol-formaldehyde copoly-condensation products,meta-xylene-diphenyl oxideformaldehyde copoly-condensation products,diphenyl-formaldehyde polycondensation products, diphenyl-alkylphenolcopoly-condensation products, substituted phenol-formaldehydepoly-condensation products, substituted phenol-diphenyloxide-formaldehyde copoly-condensation products, methacrylic esterpolymers, acrylonitrilestyrene copolymers, nitrocellulose,ethylcellulose, polyester resins and polycarbonate resins, having amolecular weight of about 600 to 5000.

Alternatively, a particulate mixture in water dispersed form is obtainedby liquidizing the organic acid substance and high molecular compound byheating or addition of an organic solvent, dispersing in water theresultant, and cooling same or if necessary, removing the organicsolvent.

Further alternative method includes the steps of mixing the organic acidsubstance and an initiator and regulator for polymerization with a vinylmonomer capable of dissolving the organic acid substance, such asstyrene, oz-methylstyrene, ethylacrylate and methylmethacrylate, andeffecting a suspension or emulsion polymerization in water thereby toobtain a particulate mixture consisting of the organic acid substanceand organic high molecular compound.

Furthermore, an alternative method for obtaining the particulate mixtureincludes the steps of adding an alkali metal or ammonium salt ofaromatic carboxylic acids into an emulsion of organic high molecularcompounds, for example polystyrene emulsion and styrenebutadienecopolymer emulsion, further adding an acid or an aqueous solution ofpolyvalent metal salts thereto and effecting an acid decomposition ordouble decom- 12 position. In this case, heating may be effected inorder to promote the diffusion of the aromatic carboxylic acid orpolyvalent metal salt thereof into the particles of the emulsifiedorganic high molecular compound. A finely pulverized mixture is thusobtained in the form of an emulsion or dispersion in water.

In many cases, according to the invention, the organic acid substanceand organic high molecular compound completely dissolve with each otherand form a homogeneous phase, but even though non-dissolving portionsare in part present in the homogeneous phase, it does not at allobstruct the objects of the invention. The fine powders obtained arecontrolled to a particle size of normally less than several microns,preferably about 0.5 ;1..

In some of the methods for preparation of the particulate mixturecomprising the organic acid substance and organic high molecularcompound, the particulate mixture may be further incorporated with atleast one of a water-insoluble inorganic material, in the form ofparticles, such as oxides, hydroxides and carbonates of a metal, andother mineral pigment, and an organic material in form of powder such aspowdered starch, powdered celluloses and organic pigments. For example,in incorporating the organic acid substance with the organic highmolecular compound under heating, a water-insoluble inorganic materialin form of particles such as clay, kaolin, activated clay, zinc oxide,calcium carbonate and aluminum hydroxide is further incorporatedtherewith, solidified by cooling and pulverized. Thus, a particulatesubstrate in which the mixture of the organic acid substance and organichigh molecular compound is adsorbed around the inorganic powders isobtained. The additional incorporation of the inorganic powders bringsabout extending effect for the particulate substrate and improvement influidity of coating composition. Particularly, the incorporation of theinorganic powders, as mentioned hereinafter, improves a color-formingproperty of the organic acid substance as well as resistance of asensitized sheet toward the sun light. An incorporation amount of theinorganic or organic powders is not particularly limited so far as thenature of the organic acid substance does not recede. It is usuallypreferred to incorporate the inorganic and/or organic powders in anamount of less than 2000 parts by dry weight based on parts by dryweight of the organic acid substance.

For the purposes of improving the compatibility between the organic acidsubstance and organic high molecular compound and also the color-formingproperty, it is preferred to further incorporate an aliphatic carboxylicacid and/or polyvalent metal salt thereof into the particulatesubstrate.

Examples of the aliphatic carboxylic acid include a saturatedmonocarboxylic acid represented by the formula, C I-I ,COOI-I wherein nis an integer, for example valeric acid, caproic acid, caprylic acid,capric acid, lauric acid, myristic acid, palmitic acid, stearic acid ora petrochemically derived synthetic fatty acid, an unsaturated or cyclicmono-carboxylic acid represented by the formula, C,,I-I ,,,COOH whereinn is an integer and m is an integer of l, 3, 5, 7 or 9, for example,acrylic acid, crotonic acid, oleic acid, elaidic acid, erucic acid,linolic acid, linolenic acid, eleostearic acid, phenylacetic acid ornaphthylacetic acid, a monooxyfatty acid such as lactic acid, ricinolicacid or oxystearic acid, a halogenated fatty acid such asa-dichloropalmitic acid chlorostearic acid and a,a-dichlorostearic acid,a poly-fattyacid such as oxalic acid, malonic acid, succinic acid,glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid,maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconicacid, glutaconic acid, malic acid and citric acid, and halogenatedproducts thereof, phenoxyacetic acid, a nucleus substitutedphenoxyacetic acid, maleic acid copolymers, an unsaturated fatty acidpolymer or an unsaturated carboxylic acid copolymer, and rosin.

A metal salt of the above aliphatic carboxylic acids may be also usedfor the same purpose as mentioned above. These compounds include saltsof all the metals which can form the salts with the above fattyacids.The aliphatic carboxylic acids and metal salts thereof may be preferablyused in an amount of less than about 100 parts by dry weight in respectof 100 parts by dry weight of the organic acid substance and organichigh molecular compound in total.

A coating composition according to the invention is obtained bydispersing the particulate mixture comprising the organic acid substanceand organic high molecular compound, if necessary, with a suitablebinder into water or a suitable organic solvent which does not easilydissolve the organic acid substance and high molecular compound. Such anorganic solvent is exemplified by methanol, ethanol, isopropanal,ethylene glycol and propylene glycol, and may be used in mixture withwater. Examples of the binder include starch, casein, gelatine, gumarabic, polyvinyl alcohol, polyacrylamide, acrylamidemethylol acrylamidecopolymer, acrylamide-acrylonitrile copolymer, methylolacrylamideacrylicester copolymer, acrylamide-acrylic ester copolymer, acrylicacid-acrylic ester copolymer, methyl cellulose, melamine resins, urearesins, sodium polyacrylate, carboxymethyl cellulose, car'boxyethylcellulose, natural rubber, synthetic rubber, polyacrylic acid ester,polymethacrylic acid ester, polyvinyl acetate, vinyl acetate-ethylenecopolymer, polypropylene, polystyrene, polyisobutylene, vinylchloride-vinyl acetate copolymer, methyl cellulose, ethyl cellulose,nitrocellulose, cellulose acetate, phenol resins, butyral resins,petroleum resins and alkyd resins.

The binders particularly water-soluble binders can be added withchemical linking agents for forming waterinsoluble binders by thereaction.

If an aqueous coating composition is desired, a water insoluble binderis used in the condition of suspension or emulsion in water.

A carboxyl-modified polymer emulsion is particularly preferred becauseit is quite stable in coatings and shows sufficient adhesive property ina small quantity. Examples of such an emulsion are carboxylatedstyrene-butadiene copolymer emulsion, carboxylatedmethylmethacrylate-butadiene emulsion and vinyl acetate-crotonic acidcopolymer emulsion. In many cases the binders are used in a mixture oftwo or more, and a suitable combination of water-soluble andwaterinsoluble binders is usually used.

The coating composition of the invention may contain water-insolubleoxides, hydroxide and carbonates of a metal and/or other mineralpigments. Particularly such metal compounds as oxides, hydroxides andcarbonates of a polyvalent metal exhibit an excellent col or-formingproperty in co-existence with the aromatic carboxylic acids. Therefore,these metal compounds are quite effective to be used in combination withsome of aromatic carboxylic acids which are considered asdisadvantageous in practice because of an inactive 14 color reaction andlow color density. Suitable inorganic metal compounds are oxides,hydroxides, and carbonates of such a metal as magnesium, calcium,barium, zinc, titanium, aluminum, nickel, cobalt, manganese, iron, tin,chromium, and palladium, and for example, magnesium oxide, calciumoxide, barium oxide, zinc oxide, aluminum oxide, tin oxide, magnesiumhydroxide, calcium hydroxide, zinc hydroxide, aluminum hydroxide, tinhydroxide, magnesium carbonate, calcium carbonate and zinc carbonate areparticularly preferred.

The above inorganic metal compounds which generally belong to the classreferred to as mineral pigments have little color-forming ability bythemselves, but exhibit nevertheless the especial color-forming abilityin combination with the aromatic carboxylic acids. The above specifiedmetal compounds are, therefore, referred to especially as inorganicmetal compounds herein and distinguished from the conventional mineralpigments. The mineral pigments other than the inorganic metal compoundsto be used are exemplified by activated clay, acid clay, aluminumsilicate, zinc silicate, tin silicate, a colloidal aluminumhydrosilicate zeolite, bentonite, kaolin and talc. They are referred tomerely as mineral pigment in the invention.

The coating composition may include the above defined inorganic metalcompound and mineral pigment in an amount of l to 10,000, preferably 5to 1,000 parts by dry weight in respect of parts by dry weight of thearomatic carboxylic acid and/or polyvalent metal salt thereof. It shouldbe understood that the coating composition may contain all or a part ofthe inorganic metal compound and mineral pigment incorporated in theparticulate substrate comprising the organic acid substance and organichigh molecular compound as mentioned hereinbefore.

The desired coating compositions for some types of self-containedcopying papers contain further fine capsules enveloping the color formertherein.

The coating composition is applied on the surface of a support by theconventional coating means, for example an air knife, rolls, blades anda sizing press or said composition is printed on the support by theprinting press, for example a letter press and flexographic method. If acoating composition is of an organic solvent type, the printing methodis preferred and the coating composition may contain further aplasticizer such as tributyl phosphate, dibutyl phthalate, dioctylphthalate, butyl adipate and castor oil.

A paper of natural fibers, a paper of synthetic fibers and a film ofsynthetic polymers may be used as the support, though the paper ofnatural fibers is usually used. The support, if necessary, may be onehaving a barrier-coat of a natural or synthetic high molecularsubstance.

The sensitized sheet according to the invention has advantages asdescribed hereunder. The organic acid substance, because of beingprevented from the actions of heat, light and particularly high moistureor water by the organic high molecular compound, can maintain a stablecolor-forming ability for a long time and completely prevent the smudge.Accordingly, an organic acid substance with a relatively low molecularweight such as salicylic acid or its polyvalent metal salt which wasunsuitable for practical use can be now put to practical use.

The coating composition, because of being excellent in mechanical andthermal stability, can be preserved in a state of perfection and alsothe coating work can be easily effected. Further, it is possible toapply it on the support by a coating apparatus mounted on the papermachine so that the pressure sensitive recording sheets are obtained inextremely economical way.

The particular mixture comprising the organic acid substance and organichigh molecular compound can be pulverized to fine powders with anuniform particle size of several microns by the mechanical means, forexample ball milling. It is, therefore, possible to form a coating layerin which the fine powders are homogeneously dispersed so that clearimages free of bleeding are obtained.

The coating composition is usually applied in an amount of more thanabout 2g/m and the upper limit is confined by a mere economical reason.

The invention is illustrated by non-limitative Examples to follow.Amounts of formulation are given in parts by dry weight unless otherwiseindicated.

EXAMPLE 1 100 parts of a thermoplastic modified xylene resin with asoftening point of l C (solid as Nikanol S-l00 by Mitsubishi GasChemistry Co., Japan) were heated to 180C, added with 90 parts of zinc3,5-di(a,adimethylbenzyl) salicylate while stirring, and dissolved. Amass was obtained by cooling and solidifying the mixture. The mass wascoarsely crushed and then pulverized with 200 parts of kaolin and 30parts of a powdered silicic anhydride (sold as Carplex No. 80 byShionogi Pharmaceutical Co., Japan) in a ball mill for hours. Aparticulate mixture with an average particle size of about 3 ,u. were,thus, obtained. The total contents of the ball mill were added with 40parts of a soluble starch and 100 parts of styrene-butadienecopolymerization latex (solids, 50%) to 600 parts of water and stirredthoroughly. A coating composition was, thus, obtained. A sensitizedsheet was obtained by applying the coating composition on the surface ofa continuously running paper web of SOg/m in an amount of IOg/m by dryweight, using a pilot paper machine (sold as RlSSAR PAPER MACHINE byMitsubishi Kakoki Co. Japan) provided with the similar coater to acommercial coater in large scale.

The coating composition was applied on the surface of a preheated paperweb and recycled during the coating work. As the result the coatingcomposition was subject to mechanical shearing and concurrently reachedthe temperature of 70C at the highest, but maintained a markedly stablefluidity without increase of viscosity.

EXAMPLE 2-1 2-14 100 parts of oz-methylstyrene-styrene copolymer with amolecular weight of about 1500 obtained by polymerization of 60 wt.% ofoe-methylstyrene and 40 wt.% of styrene in the presence of thioglycolicacid were incorporated into and melted with 200 parts of each of organicacid substances as given hereunder at temperatures of 150 to 190C toform a homogeneous liquid phase. An easily crushable mass was obtainedby cooling the liquid phase.

Example No. Organic acid substances 2-1 3,5-di-(a-methylbenzyl)salicylic acid 2-2 Zinc 3-phenyl-5-(a,a-dimethylbenzyl) salicylate 23Aluminum 3-phenyl-5-(a,a-dimcthylbenzyl) salicylate 2-4 Zinc3-cyclohexyl-5-(mot-dimethylbenzyl) salicylate 2-5 Zinc salt of3-cyclohexyl-5-(a,a-

dimethylbenzyl) salicylic acid weight and its aluminum salt 30 weight2-6 Zinc 3,5-di-(a,a-dimethylbenzyl) salicylate 2-7 Zinc salt of3,5-di-(a,a-dimethylbenzyl) salicylic acid 70 weight and its aluminumsalt 30 weight 2-8 Zinc 3-(a-methylbenzyl )-5-(a,a-dimethylbenzyl)salicylate 2-9 Zinc salt of 3-(amethylbenzyl)-5-(a,a-

dimethylbenzyl) salicylic acid 70 weight and its aluminum salt 30 weight2-11 Zinc 3-(a,a-dimethylbenzyl)-5-phenyl salicylate 2-12 Aluminum3-(a,a-dimethylbenzyl )-5-phenyl salicylate 2-13 Zinc salt of3-(a,a-dimethylbenzyl)-5- phenyl salicylic acid 70 weight 7: and itsaluminum salt 30 weight 70 2-14 Zinc 3,5-dicyclohexyl salicylate 200parts of each of the mass thus obtained were crushed to an averageparticle size of about 200 u, incorporated with one part of aformaldehyde-sodium naphthalenesulfonate condensate (sold as Demol-N byKao Atlas Co. Japan), 600 parts of water and 20 parts of a solublestarch, and then passed through a sand grind mill. Finally, 40 parts ofa styrene-butadiene copolymerization latex (solids, 50%) were addedthereto to obtain various coating compositions.

Sensitized sheets were obtained by applying each of the coatingcompositions on a support in an amount of 7g/m by dry weight in the samemanner as in Example 1. All of the coating compositions exhibited anexcellent mechanical and thermal stability during the coating work.

EXAMPLE 3-1 3-14 200 parts of each of the mass obtained in Example 2were crushed to an average particle size of about 200 u, incorporatedwith 200 parts of kaolin, 50 parts of zinc oxide, 600 parts of water, 40parts of a soluble starch and one part of Demol-N (see Example 2), andthen pulverized in a sand grind mill. Finally, 100 parts of acarboxylated styrene-butadiene copolymerization latex (solids, 50%) wereadded thereto the obtained various coating compositions.

Sensitized sheets were obtained by applying each of the coatingcompositions on a support in an amount of lOg/m by dry weight in thesame manner as in Example 1. All of the coating composition exhibitedthe same mechanical and thermal stability as in Example 1.

EXAMPLE 4 A coating composition was obtained in the same procedure as inExample 1 except that 5 parts of zinc stearate were further added in theincorporation of 100 parts of Nikanol S100 and parts of zinc3,5-di(a,adimethylbenzyl) salicylate.

A sensitized sheet was obtained from the coating composition in the samemanner as in Example 1.

EXAMPLE I00 parts of a-methylstyrene polymer with a molecular weight ofabout 1100 were heated at about 180C together with parts of zincstearate and 60 parts of zinc 3-{4'-(a,a-dimethylbenzyl)phenyl}-5-(a,adimethylbenzyl) salicylate, melted and incorporated in.The resultant was cooled, solidified and coarsely crushed. All of thecrushed products were incorporated with 40 parts of a powdered zincsilicate, parts of polyacrylamide (degree of polymerization, about 1000)and 500 parts of water and pulverized in a porcelain ball mill for about20 hours. Finally, 60 parts of a styrene-butadiene polymerization latexwere added thereto to form a coating composition.

A sensitized sheet was obtained from the coating composition in the sameprocedure as in Example 1. The coating composition exhibited a goodmechanical and thermal stability during the coating work.

EXAMPLE 6-l 6-14 100 parts of a novolak type p-phenylphenolformaldehydepolycondensation product (molecular weight, about 800) were incorporatedinto and melted with 150 parts of each of the organic acid substances asindicated hereunder at temperatures of 100 200C. A mass was obtained bycooling and solidifying the resulting liquid.

Example No. Organic acid substances Zinc 4-octoxylhenzoate Zinc 3 phenylsalicylate 4-tertiary-butylbenzoic acid Zinc 5-(3'-carboxy4'-hydroxybenzy|) salicylate 5-(3' carboxy-4"hydroxybcnzyi) salicylicacid Magnesium 3,5-di'tertiary-butyl-salicylate l carboxy-Z.3-dihydroxy6-(01,04 dimethylbenzyl) naphthalene 50 weight 70 andl-carboxy-2,3-dihydroxy-7-(11,01- dimethylbenzyl) naphthalene 50 weightEach of the mass was crushed to powders with a particle size of about200 a. 200 parts of each of the powdered substances were incorporatedwith 50 parts of zinc oxide, 600 parts of water and 40 parts of asoluble starch and pulverized in a sand grind mill. Finally, 100 partsof a carboxylated styrene-butadiene copolymer latex (solids, 50%) wereadded to form a coating composition. A sensitized sheet was obtained byapplying the coating composition on a support in the same manner as inExample 1. Each of the coating compositions exhibited the samemechanical and thermal stability as that of Example 1.

EXAMPLE 7 100 parts of polystyrene with a molecular weight of about1000, 50 parts of aluminum 3-(a,a-dimethylbenzyl)-5-cyclohexylsalicylate and 300 parts of kaolin were heated at 180C,melted and incorporated in. A mass was obtained by cooling andsolidifying the resul- 18 tant. The mass was coarsely crushed, thenincorporated with 520 parts of an aqueous solution containing 20 partsof polyvinyl alcohol and pulverized in a ball mill for 20 hours.Finally, 20 parts of a styrene-butadiene copolymer latex (solids, 50%)were added to form a coating composition.

A sensitized sheet was obtained from the coating composition in the sameprocedure as in Example 1. The coating composition exhibited the samemechanical and thermal stability as that of Example 1.

EXAMPLE 8 100 parts of a-methylstyrene polymer with a molecular weightof about 1000, 50 parts of 3-cyclohexyl-5- (a,a-dimethylbenzyl)salicylic acid, 3 parts of stearic acid and 30 parts of zinc oxide wereheated at 170C, melted and incorporated in. The resultant was cooled andsolidified to form a mass. The mass obtained was coarsely crushed, addedwith 500 parts of an aqueous solution containing 20 parts of starch andthen pulverized in a ball mill for 10 hours. Finally, 50 parts of astyrene-butadiene copolymer latex (solids, 50%) were added to form acoating composition.

A sensitized sheet was obtained from the coating composition in the sameprocedure as in Example 1. The coating composition exhibited the samemechanical and thermal stability as that of Example 1.

EXAMPLE 9 100 parts of polystyrene with a molecular weight of about 2000obtained by a polymerization in carbon tetrachloride and 100 parts ofaluminum 3,5-di( a-methylbenzyl) salicylate were incorporated and meltedat about 150C, then cooled and solidified. The mass obtained was crushedto granules with a particle size of less than about 1000 ;1., added with400 parts of kaolin and 100 parts of zinc oxide, and pulverized in aball mill for 10 hours. All of the milled products were dispersed in asolution consisting of 200 parts of water, 800 parts of ethanol and 100parts of ethylcellulose to form an ink composition.

A sensitized sheet was obtained by printing the ink composition on asupport with a weight of 50 g/m in an amount of 7 g/m by dry weightusing the usual printing machine.

EXAMPLE 10 100 parts of a styrene allylalcohol copolymer (monomer weightratio l0, molecular weight about 3,000) and 200 parts of zinc3,5-di-(a-methylbenzyl) salicylate were dissolved in 200 parts ofacetone. The acetone was, then, evaporated to obtain a mass. The masswas coarsely crushed to a particle size of about 200 a, and 200 parts ofthe crushed products were incorporated with 1 part of Demol-N (seeExample 2), 600 parts of water and 20 parts of a soluble starch andpulverized in a grinder (sold as Attritor by Mitsui Miike Seisakusho,Japan). Finally, 40 parts of styrene-butadiene copolymer latex (solids,50%) were added to form a coating composition.

A sensitized sheet was obtained with use of the coating composition inthe same manner as in Example 1.

EXAMPLE 1 l parts of a styrene-allylalcohol copolymer (monomer weightratio 85 l5 molecular weight about 1500) and 300 parts of zinc 3,S-di-(a-methylbenzyl) salicylate were dissolved in 300 parts ofacetone. The solution 19 obtained thus was little by little added to adispersion consisting of 2500 parts of water, 30 parts of Demol-N and500 parts of kaolin while stirring whereby a dispersion of a particulatesubstrate consisting of the styreneallylalcohol copolymer and zinc3,5-di-(a-methylbenzyl) salicylate was obtained. A sensitized sheet wasobtained by applying the dispersion on a support of 50 g/m in weight inan amount of 7 g/m by dry weight.

EXAMPLE 12 To 200 parts of a polystyrene emulsion (solids, 50%) wereadded 100 parts of a 30% aqueous solution of sodium3-(a,a-dimethylbenzyl)-5-methyl salicylate, heated to a temperature of80C and added little by little with 500 parts of a 40% aqueous solutionof stannous chloride while stirring. Thereafter, stirring was furthereffected for about one hour while maintaining a temperature the solutionat 90C. The emulsified polystyrene particles obtained herein contain tin3-(a,adimethylbenzyl)--salicylate. Next, 150 parts of kaolin, 100 partsof water and 30 parts of a soluble starch were added to the aboveemulsion while vigorously stirring whereby a coating composition wasobtained.

A sensitized sheet was obtained with use of the coating composition inthe same procedure as in Example 1.

EXAMPLE 13-1 l3-9 100 parts of zinc' 3,5-di(ot-methylbenzyl) salicylatewere incorporated in and melted with 50 parts of each of the organichigh molecular compounds as indicated hereunder. The resultant wascooled and solidified, thus a mass being obtained.

polycondensation product (molecular weight 700) 60 weight 70 andisophthalic acidethylene glycol polycondensation product (molecularweight L800) 40 weight Each of the above mass was coarsely crushed. 150parts of each of the crushed products were incorporated with 75 parts ofkaolin, 35 parts of activated clay, 450 parts of water and 30 parts of asoluble starch and pulverized in a sand grind mill. Finally, 75 parts ofa styrene-butadiene copolymer latex (solids, 50%) were added to form acoating composition. A sensitized sheet was obtained from the coatingcomposition in the same procedure as in Example 1. The coatingcomposition exhibited a good mechanical and thermal stability likeExample 1.

For comparison with the above Examples an aqueous dispersion of organicacid substance containing the 20 composition as indicated hereunder wasprepared separately.

A sensitized sheet was obtained by applying each of the above dispersionon a support of 50 g/m in weight in an amount of 7 to 10 g/m by dryweight according to the same procedure as in Example 1.

For confirming effects of the sensitized sheets of the invention, anupper sheet coated with micro-capsules enveloping a color former thereinwas prepared. The micro-capsules may be prepared in accordance with, forexample, US. Pat. No. 2,800,457. An embodiment for the preparation isgiven hereunder.

30 parts of an acid treated gelatin were added to 470 parts of water anddissolved at 60C. 3 parts of Crystal Violet Lactone were dissolved in100 parts of isopropylnaphthalene, warmed at 60C,'and added with theabove obtained aqueous solution of gelatin, which were then emulsifiedand dispersed with stirring to form oil droplets with an averageparticle size of 4 to 5 1a.. Next, 300 parts of a 10% aqueous solutionof gum arabic were added to the above emulsion, further added with 200parts of water, and thereafter a pH of the dispersion was adjusted tothe range of 4 to 4.5 by adding acetic acid. The dispersion was cooledto 10C to allow a coacervate film to gel and added with 10 parts offormaldehyde. After ageing for 10 hours a capsule dispersion was formed.An upper sheet was obtained by applying the dispersion on a supportpaper of 50 g/m in weight in an amount of 5 g/m by dry weight.

Effects of the sensitized sheets of the invention were confirmed by themanners to follow. A sensitized sheet subjected to the treatments asmentioned hereunder and a sensitized sheet not subjected respective wereplaced under an upper sheet carrying the encapsulated color former insuch a way that the coated surface is in contact with themicro-capsules, and a marking pressure by means of a typewriter wasapplied. Stabilities of color-forming ability toward heat, light andmoisture were observed by differences in density of a developed colorimage between the treated and untreated sheets a. Allowing a sensitizedsheet to stand in surroundings of a relative humidity and temperature of50C for 10 hours.

21 b. Allowing a sensitized sheet to stand in surroundings of 100C in atemperature for 5 hours. c. Exposing a sensitized sheet direct to thesun for 3 hours.

22 tests were made. The upper sheet was placed over the sensitized sheetin such a way that the coated surface and the micro-capsules areopposite to each other, and

, 'a marking pressure by means of a typewrlter was ap- A f h b t t d h tw A 5 plied. After standing for 24 hours the sensitized sheet b mm 6 a r:53; a Sens s was sub ect to the treatments to follow and a lowermg mug056 gz ee m 1n denslty of the color image was observed. a Way t i 6coat; f mtg-O i i g a. Allowing a sensitized sheet to stand insurroundare opposl e to 0 er lppmg e e ings of a 90% relative humidityand 50C in a temset of sheets was dried and separated to each. In case a10 r t f 10 h r d heet has low resistance toward water the pe uie or m fh h f d b. Allowmg a sensltlzed sheet to stand in surrounds O i Pa f eetorms a CO or an mgs of 100C in a temperature for 5 hours. t t ere ansest e Sm] ge c. Exposing a sensitized sheet direct to the sun for 3 Theresults of the above mentioned tests are given in hours. Table 1 15 d.Dipping a sens1t1zed sheet 1n water and drymg at For confirmingstabilities of a developed color image normal temperature. toward light,heat, moisture and water, the following The results of the above testsare given 1n Table 1.

Table 1 Stability of Stability of Color-forming Ability Developed ColorImage Example Mois- Ther- Mois- Ther- Color No. ture mal Light Waterture mal Light Water Intensity Resis- Resis Resis- Resis- Resis- Resis-Resis- Resisof the tunce tance tance tance tance tance tance tance Image1 B A A A B A B B A 2-1 B A A A B A B B C 2-2 B A A A B A B B A 2-3 B AB A B A B B B 2-4 B A A A B A B B A 2-5 B A B A B A B B B 2-6 B A A A BA B B A 2-7 B A B A B A B B B 2-8 B A A A B A B B A 2-9 B A B A B A B BB 2-10 B A A A B A B B A 2-11 B A A A B A B B A 2-12 B A B A B A B B B2-13 B A B A B A B B B 2-14 B A A A B A B B A 3-1 A A A A A A B B B 3-2A A A A A A B B A 3-3 A A B A A A B B B 3-4 A A A A A A B B A 3-5 A A BA A A B B B 3-6 A A A A A A B B A 3-7 A A B A A A B B B 3-8 A A A A A AB B A 3-9 A A B A A A B B B 3-10 A A A A A A B B A 3-11 A A A A A A B BA 3-12 A A B A A A B B B 3-13 A A B A A A B B B 3-14 A A A A A A B B A 4B A B A A A B A A 5 B A B A A A B A A 6-1 B A A A B A B A B 6-2 A A A AB A B A A 6-3 B A A A B A B A B 6-4 A A A A B A B A A 6-5 A A A A B A BA A 6-6 A A A A B A B A A 6-7 A A A A B A B A A 6-8 A A A A B A B A A6-9 A A A A B A B A A 6-10 B A A A B A B A B 6-1 1 A A A A B A B A A6-12 B A A A B A B A B 6-13 A A A A B A B A A 6-14 B A A A B A B A B 7 BA B A A A B A B s B A A A A A A A B 9 B A A A B A B A B 10 B A B B B A BA A 11 B A A A B A B A A 12 B A A B B A A B B 13-1 B A A A B A B B A13-2 A A B A A A B A A 13-3 A A B A A A B A A 13-4 B B B A B B B A B13-5 B A A A B A A B A 13-6 B A A A B A B A A 13-7 A A B A A A B A A 138B A A A B A B B A 13-9 B A A A B A A B A Table l-continued Stability ofStability of Co|orforming Ability Developed Color Image Example Mois-Ther- Mois- Ther- Color No. ture mal Light Water ture mal Light WaterIntensity Resis- Resis- Rcsis- Resis- Resis- Resis- Resis- Resis of thelance tancc tance tance tancc tance tance tance Image Control I C B B DC B B D C 2 C A B D C A B D B 3 C A B D C A B D A 4 C A B B C A C B AStability of colorforming ability A: maintained its originalcolor-forming ability B: scarcely deteriorated C: remarkablydeteriorated D: entirely deteriorated (color images could not be formed)Stability of developed color image A: not changed in color at all B:scarcely faded C: remarkably faded D: faded or discolored Colorintensity of the image A: high B: average C: extremely low We claim:

1. A process for the production of a sheet material for use in apressure-sensitive copy system which comprises applying on a supportsheet a suspension of a particulate mixture comprising (a) 100 parts byweight of an acidic organic substance selected from the group consistingof aromatic carboxylic acids and polyvalent metal salts thereof, and (b)from 5 300 parts by weight of an organic high molecular compoundselected from the group consisting of polystyrene, styrene copolymers,a-methylstyrene polymer, a-methylstyrene copolymers, polyvinyl chloride,vinylchloride copolymers, vinylidenechloride copolymers,polychloroprene, cyclopentadiene polymers, cyclopentadiene copolymers,acrylic ester polymers, acrylic ester copolymers, acrylic acidcopolymers, methacrylic ester polymers, methacrylic ester copolymers,methacrylic acid copolymers, vinylacetate polymers, vinylacetatecopolymers such as ethylene-vinylacetate copolymer, acrylonitrilecopolymers, acrylamide copolymers, allylalcohol copolymers,benzylchloride polycondensation products, benzylchloridecopolycondensation products, meta-xylene-formaldehyde condensates,diphenyl-formaldehyde condensates, and diphenyl-metalxylene-formaldehydecopolycondensation products, said organic high molecular compound havinga molecular weight of at least 400 and a non-fluidic property at normaltemperature and being compatible-with said acidic organic substance, andthereafter drying.

2. Process for the production of sheet material according to claim 1,wherein said suspension further contains at least one of awater-insoluble inorganic ma terial, in form of particles, selected fromthe group consisting of inorganic metal compounds and mineral pigments.

3. Process for the production of sheet material ac cording to claim 2,wherein said water-insoluble inorganic material is present in mixturewith the said particulate size.

4. process for the production of sheet material according to claim 2,wherein said waterinsoluble inorganic material is present in a weightratio of from 1 to 10,000 parts to 100 parts of said organic acidicsubstance.

5. Process for the production of sheet material according to claim 2,wherein said water-insoluble inorganic material is present in mixturewith the particulate mixture in a weight ratio of not more than 2,000parts to 100 parts of said organic acidic substance.

6. Process for the production of sheet material, according to claim 1,wherein said particulate mixture is obtained by mixing and melting theorganic acidic substance and organic high molecular compound whileheating, solidifying the resultant by cooling, and then pulverizing it.

7. Process for the production of sheet material, according to claim 6,wherein said organic acidic substance and organic high molecularcompound are mixed and melted with a water-insoluble inorganic materialin form of particles while heating.

8. Process for the production of sheet material according to claim 1,wherein said particulate mixture is obtained by dissolving the organicacidic substance and organic high molecular compound in an organicsolvent therefor and mixing same, evaporating the resultant to dryness,and then pulverizing it.

9. Process for the production of sheet material according to claim 8,wherein said organic acidic substance and organic high molecularcompound are dissolved in the organic solvent with a water-insolubleinorganic material in form of particles.

10. Process for the production of sheet material according to claim 1,wherein said particulate mixture is obtained by liquidizing the organicacidic substance and organic high molecular compound by heating oraddition of an organic solvent, dispersing in water the resultant, andcooling same or if necessary, removing the organic solvent therebyobtaining a particulate mixture in water-dispersed form.

11. Process for the production of sheet material according to claim 1,wherein said particulate mixture is obtained by mixing the organicacidic substance, an initiator and regulator for polymerization with avinyl monomer capable of dissolving the organic acidic substance, andeffecting a suspension or emulsion polymerization in water.

12. Process for the production of sheet material according to claim 1,wherein said particulate mixture is obtained by adding an alkali metalsalt or ammonium salt of aromatic carboxylic acid into an emulsion ororganic high molecular compounds, further adding a acid or an aqueoussolution of polyvalent metal salts thereto, and effecting an aciddecomposition or double decomposition thereby obtaining a particulatemixture in water-emulsified form.

1. A PROCESS FOR THE PRODUCTION OF A SHEET MATERIAL FOR USE IN APRESSURE-SENSITIVE COPY SYSTEM WHICH COMPRISES APPLYING ON A SUPPORTSHEET A SUSPENSION OF A PARTICULATE MIXTURE COMPRISING (A) 100 SELECTEDFROM THE GROUP CONSISTING OF AROMATIC CARBOXYLIC ACIDS AND POLYVALENTMETALS SALTS THEREOF, AND (B) FROM 5-300 PARTS BY WEIGHT OF AN ORGANICHIGH MOLECULAR COMPOUND SELECTED FROM THE GROUP CONSISTING OFPOLYSTYRENE, STYRENE COPOLYMERS, A-METHYLSTYRENE POLYMER,A-METHYLSTYRENE COPOLYMERS, POLYVINYL CHLORIDE, VINYLCHLORIDECOPOLYMERS, VINYLIDENECHLORIDE COPOLYMERS, POLYCHLOROPRENE,CYCLOPENTADIENE POLYMERS, CYCLOPENTAADIENE COPOLYMERS, ACRYLIC ESTERPOLYMERS, ACRYLIC ESTER POLYMERS, METHACRYLIC ESTER COPOLYMERS,METHACRYLIC ESTER POLYMERS, METHACRYLIC ESTER COPOLYMERS, METHACRYLICACID COPOLYMERS, VINYLACETATE POLYMERS, VINNYLACETATE COPOLYMERS SUCH ASETHYLENE-VINYLACETATE COPOLYMER, ACRYLONITRILE COPOLYMERS, ACRYLAMIDECOPOLYMERS, ALLYLACOHOL COPOLYMERS, BENZYLCHLORIDE POLYCONDENSATIONPRODUCTS, BENZYLCHLORIDE COPOLYCONDENSATION PRODUCTS,META-XYLENE-FORMALDEHYDE CONDENSATES, DIPHENYL-FORMALDEHYDE CONDENSATESAND DIPHENYL-METAL-XYLENEE-FORMALDEHYDE COPOLYCONDENSATION PRODUCTS,SAID ORGANIC HIHG MOLECULAR COMPOUND HAVING A MOLECULAR WEIGHT OF ATLEAST 400 AND A NON-FLUIDIC PROPERTY AT NORMAL TEMPERATURE AND BEINGCOMPATIBLE WITH SAID ACIDIC ORGANIC SUBSTANCE, AND THEREAFTER DRYING. 2.Process for the production of sheet material according to claim 1,wherein said suspension further contains at least one of awater-insoluble inorganic material, in form of particles, selected fromthe group consisting of inorganic metal compounds and mineral pigments.3. Process for the production of sheet material according to claim 2,wherein said water-insoluble inorganic material is present in mixturewith the said particulate size.
 4. process for the production of sheetmaterial according to claim 2, wherein said water-insoluble inorganicmaterial is present in a weight ratio of from 1 to 10,000 parts to 100parts of said organic acidic substance.
 5. Process for the production ofsheet material according to claim 2, wherein said water-insolubleinorganic material is present in mixture with the particulate mixture ina weight ratio of not more than 2,000 parts to 100 parts of said organicacidic substance.
 6. Process for the production of sheet material,according to claim 1, wherein said particulate mixture is obtained bymixing and melting the organic acidic substance and organic highmolecular compound while heating, solidifying the resultant by cooling,and then pulverizing it.
 7. Process for the production of sheetmaterial, according to claim 6, wherein said organic acidic substanceand organic high molecular compound are mixed and melted with awater-insoluble inorganic material in form of particles while heating.8. Process for the production of sheet material according to claim 1,wherein said particulate mixture is obtained by dissolving the organicacidic substance and organic high molecular compound in an organicsolvent therefor and mixing same, evaporating the resultant to dryness,and then pulverizing it.
 9. Process for the production of sheet materialaccording to claim 8, wherein said organic acidic substance and organichigh molecular compound are dissolved in the organic solvent with awater-insoluble inorganic material in form of particles.
 10. Process forthe production of sheet material according to claim 1, wherein saidparticulate mixture is obtained by liquidizing the organic acidicsubstance and organic high molecular compound by heating or addition ofan organic solvent, dispersing in water the resultant, and cooling sameor if necessary, removing the organic solvent thereby obtaining aparticulate mixture in water-dispersed form.
 11. Process for theproduction of sheet material according to claim 1, wherein saidparticulate mixture is obtained by mixing the organic acidic substance,an initiator and regulator for polymerization with a vinyl monomercapable of dissolving the organic acidic substance, and effecting asuspension or emulsion polymerization in water.
 12. Process for theproduction of sheet material according to claim 1, wherein saidparticulate mixture is obtained by adding an alkali metal salt orammonium salt of aromatic carboxylic acid into an emulsion or organichigh molecular compounds, further adding a acid or an aqueous solutionof polyvalent metal salts thereto, and effecting an acid decompositionor double decomposition thEreby obtaining a particulate mixture inwater-emulsified form.